(1) Field of the Invention
The present invention relates to composite ceramic sintered bodies. More particularly the invention relates to porous composite ceramic sintered bodies to be suitably used as electric materials, structural materials, and ceramic products such as filters. The invention also relates to a process for producing the same.
(2) Related Art Statement
Since aluminum nitride ceramics have various properties such as high heat resistance, high electric insulation, high heat conductivity and high corrosion resistance, aluminum nitride ceramics have been formerly used as electric materials for semiconductor heat-emitting plates and circuit boards, structural materials for members in semiconductor producing apparatuses, and filters disclosed in JP-A-5-246,775 and JP-A-6 327,921.
In order to use such an aluminum nitride ceramic material for a filter, as described in JP-A-5 246,775 and JP-A-6 327,921, a technique is proposed where carbon or an organic foaming agent is preliminarily mixed into the aluminum nitride ceramic material, which is sintered to make the resulting product porous by removing the additive.
However, such a porous aluminum nitride ceramic product must be produced at a sintering temperature lower than that at which a dense bulky aluminum nitride product is produced.
Therefore, the above technique has problems in that sintering is insufficient, which makes heat conductivity and heat impact resistance lower. Further, since strength and toughness drop, machinability are deteriorated.
Further, there is other problem in that ammonia having pungent smell is generated through reaction between aluminum nitride and moisture in air.